a b s t r a c tChemical composition and liberation are critical attributes in characterizing a resource stock for beneficiation investigations. Though end-of-life printed circuit board is recognized as a valuable secondary resource stock, no procedural standard exists for the determination of its chemical composition, nor for the À75 lm fines generated during its comminution. The effect of the digestion procedure on the final assays in wet spectroscopic analyses was assessed in this work. Liberation was also explored against literature background. Determination of assays of all constituent elements in printed circuit board comminution fines was found to require comparison of data from more than one digestion condition, while composite particles still persist at the fines sizes, though very few. The discussion reflects how these impact the beneficiation investigations.

a b s t r a c tFroth flotation for beneficiation of printed circuit board comminution fines was investigated in this work, via reverse flotation under a scheme described as natural hydrophobic response. With no reagents, the scheme employed variation of kinetic parameters of airflow rate and impeller speed to optimize metallic enrichment of the sink. The impeller energy and aeration rate required to keep the pulp in suspension and avoid excessive turbulence were found to be much lower compared with conventional mineral flotation. The natural hydrophobic response was found to exist, and stable froth was observed even without the use of any frother. It was submitted that the dynamic froth stability observed is due to fine particle stabilization. Mass pulls obtained were high and cumulative mass pull under the varying kinetic regimes were found to fit very well to the general first order kinetics. The extents of fit, the sink enrichment and the recovery in respect of metallic values were assessed to evaluate the beneficiation performance. Many of the metallic elements were found to concentrate into the sink, while some prefer the froth phase. Notably, gold and palladium were among the best recovered to the sink; with about 64% recovery at enrichment ratio of 3.1 (676 ppm actual assay) for Au. The flotation scheme proved effective for PCB comminution fines, and performance improvement also looks very feasible.

Ferrovanadium is sometimes produced from V 2 O 3 in electric arc furnaces, using aluminum as a reductant. The CaO fluxes the alumina, which forms during reduction of the vanadium oxide. Incomplete reduction of vanadium oxide from the slag is a significant cause of vanadium losses. To quantify factors that can affect the equilibrium vanadium loss, the vanadium oxide activity coefficient was measured experimentally for different slag compositions. Hydrogen-water mixtures were used to control the partial oxygen pressure (approximately 10 Ϫ13 atm) over CaO-Al 2 O 3 slags contained in vanadium crucibles at 1700 ЊC; gas-phase mass transfer was controlled by jetting the gas mixture onto the slag surface. Manipulation of the redox conditions at a single slag composition and temperature showed that, as expected, the vanadium is present in the trivalent state in the slag. The slag basicity (CaO-Al 2 O 3 ratio) was found to have a very strong effect on the activity coefficient of VO 1.5 , with clear implications for the effect of plant practice on vanadium loss.

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